Rising temperatures and heat waves as drivers of Salmonella and Campylobacter bacteraemia across diverse climatic zones in Queensland, Australia

Climate change, with rising ambient temperatures and heatwaves, has been linked to an increased risk of food-borne infections. Using a time series quasi-Poisson regression with a Distributed Lag Non-Linear Model (DLNM), we examine the associations between ambient temperature and heatwaves and the risk of Salmonella and Campylobacter bacteraemia in Queensland (QLD), Australia. A total of 1034 Salmonella and 234 Campylobacter bacteraemia cases were recorded during 2010-2019. Deseasonalised mean temperatures showed a significant positive relationship with Salmonella bacteraemia in Southeast (SE) QLD and Tropical North QLD. In SE QLD, a 1 °C increase in mean temperature increased risk of Salmonella bacteraemia by 8-20% across the significant portion of the dose-response curve (RR range: 1.08-1.20, 95% CI: 1.01-1.40), while maximum temperature was linked to 0.3-16% increase (RR range: 1.003-1.16, 95% CI: 0.84-1.57). In Tropical North QLD, a 1 °C rise in mean temperature was associated with an 18% increase, peaking at 27.2 °C (RR 1.70, 95% CI: 1.01-2.86). At maximum temperatures above 28 °C, each 1 °C increase corresponded to an 11-105% rise in risk (RR range 1.11-2.05, 95% CI: 1.01-4.73). In Central QLD, Salmonella risk exhibited a modest upward trend across temperature ranges of 11 °C to 17.5 °C (mean) and 16 °C to 22 °C (maximum), but estimates were not statistically significant. Cases peaked within one week in SE QLD and after three weeks in Tropical North QLD. Heatwave exposure increased Salmonella bacteraemia cases by 31% per degree rise in maximum temperature (IRR: 1.31, 95% CI: 1.16-1.48), reflecting the heatwave-specific intensity-response effects and is not directly comparable to the DLNM temperature RR estimates. No significant associations were identified for campylobacteriosis. These findings confirm the significant impact of rising ambient temperatures and heatwaves on Salmonella bacteraemia risk, underscoring the need for climate-adaptive public health strategies.